Marc Haibeck

Are the ‘95 models really that much better?

From Lotus, Brian Kid has an official road map to the changes.

Item 3. I recommend the roller pilot bearing PN 14061685.

At about the ‘92 ½

model year point, GM began installing a new oil cooler hose assembly.

10 12 mm diameter bolts 10 8 mm plus 10 10 mm

dia. bolts

‘90 –

’92

‘93 –

‘95

Dunn cylinder #1 ports. 34 mm primary.

‘91

Birmal

cylinder #1 ports. 33mm primary.

Cylinder head to injector housing port mismatch on a ‘91.

Two flats on ‘93 –

’95. +/-

1 deg. One flat on ‘90 –

’92. +/-

2

degs.

Graham

Behan

was the engineer in charge for the 1993 model year upgrade program. Graham describes more details about the upgrades for the 405 HP engine.

From the “ZR-1 Legend”

publication March 1998

The strategy.

LT1 Exhaust system.

Improved Dunn cylinder heads.

Subsequent to the publication of his article Graham added the knock sensor to the list. The structural changes to the cylinder

block altered the fundamental frequency of the block. The knock control system was revised to match.

Noise Reduction

Beginning with the ‘92 GM service manual a section about noise reduction was provided.

The list of noise sources was increased each year. Most of the remedies were implemented by ‘94. The ‘95 cars received the most attention to noise. The ‘95 service manual document s about 67 noises that may occur in the ZR-1.

A few examples…